The present invention relates to a shaping device for a flexible film, specifically, although not exclusively for making bags containing a perfusion liquid.
There are already known machines for manufacturing bags from a flexible film of plastic material. More specifically, there are known machines for manufacturing bags from a web of thermoplastic film. These machines include a series of stations at which the thermoplastic film is treated in succession. Generally, the film is unwound from a spool then perforated. Perpendicular to the perforations, ports or fitments are heat sealed by a welding head. The film is then shaped in a shaping device principally designed to fold the film back on itself in order to obtain an edge to edge sealing. The film that has been sealed edge to edge forms a tube that is then sealed in the transverse direction at regular intervals to form individual bags. Those individual bags are filled prior to manufacture of a second transverse seal which forms the bag.
The present invention relates particularly to the film shaping device, which is a station located after the positioning and sealing of the ports or fitments and prior to the sealing of the film edge to edge. French Pat. No. 2 528 801 describes a shaping device having a shaping plate extending in a direction transverse to a direction of the film. The device has a slit, preferably a U-shaped slit, with two arms joined together by a connecting portion and an opening adjacent to the slit. When the film equipped with ports or fitments has first been fed in a flat position and passes through the slit of the shaping device, it is folded back on itself and each port or fitment passes through the opening adjacent to the slit. At the exit of the shaping device, however, no special guiding is provided. A return is generally done by transverse rollers that project on each side of the film. When the ports or fitments are positioned along an edge of the shaped film, a risk exists that the flange of the port or fitment sealed to the film may press too strongly against the return roller and cause either a tearing of the film or damage to the seal between the flange and the film.